1. Field of the Invention
The present invention relates to pig launchers for launching pigs into (or launching pigs into and retrieving pigs from) an oil or gas production flowline and pigging systems incorporating the same. The present invention is particular applicable and is particularly described below in relation to launching pigs into (or launching pigs into and retrieving pigs from) an oil or gas subsea pipeline in a diverless operation. It will however be apparent to one skilled in the art that a launcher in accordance with the present invention could also be used for launching pigs into (or launching pigs into and retrieving pigs from) an oil or gas pipeline at a topside/surface location.
2. Description of Related Art
A remotely operated vehicle ROV is not well adapted to load or unload pipeline pigs into a pig launcher/receiver (PLR) at a subsea location. Pigging systems of the type in which one or more pipeline pigs are loaded at a surface location into one or more launching chambers of a pig launcher, the launcher is lowered to a subsea location where it is coupled to a subsea oil production pipeline and at least one pig is launched from a chamber into the pipeline are known. UK Patent Application 0132195739 A (British Petroleum); UK Patent Application GB2195740 A (British Petroleum); U.S. Pat. No. 6,533,032 B1 (Seixas et al.) and U.S. Pat. No. 6,336,238 B1 (Tarlton) disclose systems of this type.